Multi-electron reactivity of a cofacial di-tin(ii) cryptand: partial reduction of sulfur and selenium and reversible generation of S₃˙⁻

Abstract

A cofacial di-tin(ii) hexacarboxamide cryptand that binds sulfur to form a complex containing μ-S and bridging μ-S5 ligands and acts reversibly as a source of S3˙– in DMF solution is described.

The role of polysulfide dianions and radical anions in the chemical, physical and biological sciences, including sulfur-based batteries

“…178 Although no molecular complexes of this important sulfur ligand have been isolated and characterized, Cummins and co-workers have described the reversible generation of [S 3 ] À from a di-tin complex with bridging pentasulfido and monosulfido ligands [(m-S 5 )Sn 2 (m-S)(mBDCA-5t)] 2À (Scheme 6). 187 Solutions of this yellow polysulfido complex in DMF or DMSO are dark blue-green and exhibit the characteristic spectroscopic signatures of [S 3 ] À (a strong absorption at l max = 617 nm in the UV-visible spectrum and a broad signal centred at g = 2.0290 in the EPR spectrum). 187 The amount of [S 3 ] À in DMF solution increases as (a) the concentration of the di-tin complex is diluted or (b) the temperature is increased from 20 to 85 1C.…”

“…187 Solutions of this yellow polysulfido complex in DMF or DMSO are dark blue-green and exhibit the characteristic spectroscopic signatures of [S 3 ] À (a strong absorption at l max = 617 nm in the UV-visible spectrum and a broad signal centred at g = 2.0290 in the EPR spectrum). 187 The amount of [S 3 ] À in DMF solution increases as (a) the concentration of the di-tin complex is diluted or (b) the temperature is increased from 20 to 85 1C. The formation of the neutral di-tin complex [(m-S 5 )Sn 2 -(m-S)(mBDCA-5t)] as a result of this dissociation was proposed, but not confirmed.…”

“…The formation of the neutral di-tin complex [(m-S 5 )Sn 2 -(m-S)(mBDCA-5t)] as a result of this dissociation was proposed, but not confirmed. 187 A metal complex of the tetrasulfide radical anion [S 4 ] À was first proposed in the mid-1990s by Isobe and co-workers for the tetranuclear rhodium dication [{Rh 2 Cp* 2 (m-CH 2 ) 2 } 2 (m-S 4 )] 2+ . 188a The rectangular S 4 unit in this complex has two short and two long S-S distances of 197.9(1) and 270.2(1) pm, respectively.…”

Halide Photoredox Chemistry

“…The work on main group participation in transition metal based HX splitting has launched investigations into complexes where a main group element is the sole mediator for halogen elimination. Many main group elements in fact seem ideal for this application, as they preferably perform two-electron redox chemistry, as the one-electron processes are more energetically demanding. − Examples of halogen elimination remain uncommon, but examples of tellurium − and antimony , have been reported. An early example was T – X 2 , shown in Figure , that was reported by Seferos et al and utilized a tellurophene functional group, where the tellurium center had accessible II and IV oxidation states .…”

Second-Coordination-Sphere Assisted Selective Colorimetric Turn-on Fluoride Sensing by a Mono-Metallic Co(II) Hexacarboxamide Cryptand Complex

“…16 This cryptand behaves both as an anion receptor 17 and a ligand platform supporting cofacial bimetallic complexes of both transition and main group metal ions † Massachusetts Institute of Technology ‡ Harvard University upon hexadeprotonation. [18][19][20] Insertion of a single transition-metal ion into the cryptand provides a Lewis acidic binding site for fluoride, while the second-coordination sphere offers pre-organized hydrogen-bond-donating N-H groups. These properties create a ligand architecture reminiscent of metalloprotein active sites that contain a built-in hydrogen-bonding network stabilizing ligands bound to the metal ions.…”